INTRODUCTION: This study aims to verify the usefulness of a new model of minilaparoscopy trocar that do not have a valve or sealing membranes and therefore have a much better ratio of dynamic friction. It is well known that with a lower friction the stress of surgical movements decreases and the precision increases. There was a doubt whether the lack of valve and sealing membrane would impair the use of trocars due to the large amount of gas leak.

METHOD: Two experiments were conducted: A) In Vitro – The loss of gas was measured in a closed system. The system consisted of a gas inflator (15 l / min), a rubber ball and the 2mm and 3mm trocars, obliterated by their forceps. The pressures used were 10, 12 and 15 mmHg, in that order. Each test lasted 5 minutes and was repeated five times. Finally it was calculated the average per-minute gas loss. B – In Vivo: It was analyzed 28 patients who underwent laparoscopic (trocars of 5mm and 10mm) and minilaparoscopic (trocars of 2mm and 3mm) cholecystectomy in the University Hospital Oswaldo Cruz, Recife – PE, Brazil. The average of the total gas loss during the procedures was divided by the average operative time.

RESULTS: Experiment A: There was a significant difference between the leak of the 2mm and 3mm trocars at all tested pressures (p<0.0001). When subjected to a pressure of 12mmHg the 2mm had a leak = 0.09 l / min vs. 0.49 L / min of the 3mm trocar. The smallest leak happened to 10 mmHg: 0.08 l / min (2 mm) vs. 0.44 l / min (3mm). At 15mmHg, the loss was 0.11 l / min for the 2mm vs. 0.52 l / min for the 3mm. As it was expected, pressure and gas leak proved to be directly proportional. Experiment B: The average operative time of laparoscopic cholecystectomy was 34.9 min and the average gas loss was 123.3 liters, resulting in a loss of 3.5 l / min. On the other hand the average time of the minilaparoscopic cases were 25.8 min with an average gas loss of 95.7 liters, resulting in a leakage of 3.7 l / min (p=N.S.)

CONCLUSION: It was demonstrated that the 2 and 3mm trocars without valves and sealing membranes are viable and very useful. The experiments showed that the gas loss does not differ much from traditional trocars with valves and sealing. Moreover, the absence of valves and membranes provides a much lower friction, improves trocar dynamics, resulting in much greater precision for surgical movements.